Find the unknown entries $a, b, c, d, e, f$ in the following distribution of heights of students in a class:

Height (in $cm$)	Frequency	Cumulative frequency
$150-155$	$12$	$a$
$155-160$	$b$	$25$
$160-165$	$10$	$c$
$165-170$	$d$	$43$
$170-175$	$e$	$48$
$175-180$	$2$	$f$
Total	$50$	-

(A) To find the unknown entries,we use the definition of cumulative frequency,where each entry is the sum of the frequency of the current class and all previous classes.
$1$. For the first class $(150-155)$,the cumulative frequency is equal to the frequency: $a = 12$.
$2$. For the second class $(155-160)$,the cumulative frequency is $12 + b = 25$. Thus,$b = 25 - 12 = 13$.
$3$. For the third class $(160-165)$,the cumulative frequency is $c = 12 + b + 10 = 12 + 13 + 10 = 35$.
$4$. For the fourth class $(165-170)$,the cumulative frequency is $c + d = 43$. Substituting $c = 35$,we get $35 + d = 43$,so $d = 43 - 35 = 8$.
$5$. For the fifth class $(170-175)$,the cumulative frequency is $43 + e = 48$. Thus,$e = 48 - 43 = 5$.
$6$. For the sixth class $(175-180)$,the cumulative frequency is $f = 48 + 2 = 50$. Thus,$f = 50$.
Therefore,the values are: $a = 12, b = 13, c = 35, d = 8, e = 5, f = 50$.